Colonoscopy is currently the preferred method for colon cancer screening. This procedure is used to examine the surface of the gastrointestinal tract for abnormalities, such as polyps consisting of abnormal growth into the lumen. When detected, these polyps can be removed thus decreasing the risk of colon cancer by an estimated 75 to 90% (Davila et al., 2006). However, the colonoscopy miss rate can be over 10% (Pickhardt et al., 2004). Cancers diagnosed after a colonoscopy, also called interval cancers, have multiple possible causes including a different biology than non-interval cancers and factors related to the procedure itself. Among procedural causes, missed lesions are thought to play a large role (Cooper et al., 2011; Pohl et al., 2010; Faiss S., 2011). There has been significant focus on flat lesions and specifically sessile serrated adenomas and their possible role in interval cancer. Flat polyps especially the sessile serrated adenomas are difficult to detect and may evolve more rapidly into cancer (Anderson J., 2011; Leggett et al., 2010).
For colonoscopy to continue to be the preferred method for colon cancer screening, its sensitivity must improve. Panchromoendoscopy using dyes including Indigo carmine or Methylene blue sprayed directly onto the surface of the colon has been shown to increase the sensitivity. However chromoendoscopy has not been widely adopted because it can be cumbersome and time-consuming (Coe et al., 2012). Chromoendoscopy remains the gold standard for polyp detection and should theoretically be performed routinely (Brown S. and Baraza W., 2010). However, time constraints continue to dictate that chromoendoscopy is employed only selectively.
Indirect chromoendoscopy offers the potential for more efficient use of chromoendoscopy. With indirect chromoendoscopy, the dye is administered orally thereby eliminating the time spent spraying the colon. Indirect chromoendoscopy has been attempted in the past with giving 100 mg of oral indigo carmine in the form of a capsule or powder before ingestion of the oral preparation (Mitooka et al., 1992). However, this method has not been adopted as it does not provide enough staining to improve polyp detection rate (Araujo et al., 2002). There is a need for new methods to enhance staining during chromoendoscopy in a more time-efficient and convenient manner.